Polyperoxide catalysts in ethylene polymerization



Patented June 13, 1950 Milton J. Roedel, Wilmington, Del,

nlllgncr to E. L du Pont de Nemom I Company, Wil mlngton, M, a corp ration cit-Delaware No Drawing. Application November Serial No. 565,811

6 Claims. (Cl. zoo-94.9) I

This invention relates to improvements in the catalytic polymerization of organic compounds containing oleflnic unsaturation.

It is known that ethylene and other mono-' oleilns can be polymerized with the aid of catalysts such as oxygen, 'dialkyl dioxides, acyl per-' of unconverted ketones by washinglwith water.

'dried over sodium sulfate, and filtered.

oxides, chloramine T, manganese fdioxidaamine,

oxides, 'tetraphenyltin, tetraethyl lead, butyl v andmixtures of aldehydes,- and from mixtures of lithium, hexachlcroetha'ne, etc. 1

This invention has as an object to provide a new and improved method for polymerizing organic compounds containing at least one polymer;- producing linkage. Another. object isto provide a new process tor polymerizing organic compounds containing monooleflnic unsaturation.

Still another object is to provide'a new process for polymerizing monooleflnic hydrocarbons alone The product can be further purified by steam distillation although this step is not essential for the practice or this invention.-

As' previously indicated, the polyperoxideslof' this invention canbe made from any suitable ketone, mixture of ketones, i'rom any aldehyde aldehydes and ketones. Examples of ketones and a'ldehydes are acetone, methyl ethyl ketone, methyl isopropyl ketone,'cyclohexanone, mesityl oxide,

vjdiacetyl, acetyl acetone, diphenylketone, benzoin,

acetaldehyde, "propionaldehyde, butyraldehyde. eyclopentaldehyde, benzaldehyde, furfural, gly- .oxal, methyl glyoxal, acetylbenzaldehyde, and the and in admixture with other polymerizable or- I ganic compounds containing monooleflnic un-,-

. saturation. Further objects reside in the provi-,

sion of a class of catalysts for the polymerization of ethylene alone and in admixture with other organic compounds containing monooleiinic un saturation to produce polymers having the valuable properties hereinafter described. Other obs jects will appear asthe description proceeds. 1

The above objects are accomplished by conduct'lng the polymerization at elevated temperatures and pressures in contact with an organic polyperoxide as acatalyst.

The expression organic polyperoxide" refers compounds containing two or more peroxy lingEages,\-:Q0,and which ar obtained by reacting, under peroxide-forming conditions, either a ketone or aldehyde, .or a mixture of two The organic compounds containing a polymer producing linkage used in the process of this invention include those having carbon-oxygen unsaturation and; which are known to be polymerizable, suchas carbon monoxide, formaldehyde ketones or a mixture of two aldehydes. A typical I method for preparing these organic polyperoxides is described in Allen Property Custodian application 8. N. 307,933, filed December 6,1939, now abandoned. A-polyperoxide from acetone and methyl ethyl ketone-is made as follows: 4

About 163 cc. .0! concentrated sulfuric acidis added to 130 cc. ofwater-and after th mixture has cooled down to room temperature 113 g.'ot hydrogen peroxide of 30% concentration is added. The mixture is then cooledv to approximately -18 C. and a mixture of 36 g.- 'oi' methylethyl 'ketone and 29 g, oi! acetone is added in portions while stirring, care being takenthat the temperature of the mixture does not rise above 0 C. After addition of the ketones thev mixture is allowed to stand for about ,15 minutes and then' water is added until the total volume is ,1 liter, whereupon a colorless,- viscous upper layer separates. This layer is ireed of acid and any traces and thelike, and thosehaving carbon-to-carbon unsaturation ot the ethylenic type, namely,

' C=C Examples of these Dolymerizable organic compounds containing monoolefinic unsaturation include ethylene, propylene, the butylenes, tetrafluoroethylene, vinyl fluoride, vinylidene fluoride, vinyl chloride, vinyl. acetate, vinyl propionate, vinyl benzoate, vinyl iscbutyrate, vinyl thiolacetate, vinyl dimethyl and trimethyl acetates. vinyl laurate, vinyl hexenoate, and other organic vinyl esters. vinylidenechloride, vinyl ketonc s. e. g., methyl vinyl ketone, ethyl isonropenyl ketone, etc., styrene, acrylic and methacrylic acids and their esters, nitriles, amides and anhydrides, etc., N-vinyl imides, e. g., N-vinyl phthalimide, N-vinyl succinimide, etc.

In the practice of this invention as a batch operation, a suitable reaction vessel is charged ing a polymer producing linkage, and recording thermocouples are inserted into the vessel. The desired organic compound containing a polymerproduclng linkage is added to the reaction vessel w and heating and agitation ar started. Upon reaching reaction temperature, orafter a short period of induction, the reaction starts and is normally followed bya pressure decrease due to utilization of the organic compound containing a polymer-producing linkage. The pressure within the system is maintained throughout the reaction period either by addition of fresh organiccompound containing a polymer-producing linkage or by decreasing the free space in the reactor by increasing the volume of the medium. When reaction is complete, as evidenced by cessation of pressuie'drop, the vessel is cooled, bled of excess The polymer is isolated from the reaction mixture by means well known to the art, e.-g'., by filtering and drying. The polymer is usually in a satislactory form but it may be purified by washv polymer producing linkage, e. g., ethylene with.

another polymerizable organic compound containing monoolefinic unsaturation, e. g.,'propylene or vinyl acetate. The organic compound to be polymerized with the ethylene can be added with the catalyst, or, if it is a gas atnormal temperatures and pressures, it may be expanded from pressure storage tanks into the closed reaction vessel prior to or after pressuring with ethylene, or it may be added in admixture with the ethylene. The proportion of organic compound containin a polymer producing. linkage charged into the reaction vessel can :be varied over a wide range. Control of this variable can be had either by varying the pressure in the reaction vessel, by varying the ratio of liquid charge to the free space gas, opened and the reaction mixture discharged.

au xao an intrinsic viscosity of 0.76 (measured as a 0.125% solution in xylene at 85 C.), which corresponds to a molecular weight of about 13,400. This ethylene polymer is tough, contains an'in- I appreciable quantity of grain, is very soluble in hot xylene, and can be melt extruded readily.

. Example 2 .48 stainless steel'pressure reaction vessel is flushed-with oxygen-free nitrogen andcharged' with 88 parts oibenzene'and 0.1 .part of the acetone-methyl ethyl ketone heteropolyperoxide pre- .,Dared from a mixture of equal molar portions or in the reactor, by varying the reaction temperature, or by a combination of these.

As a rule, the amount of catalyst will range from about 0.001 to about 5% of the total weight of monomer charged intothe reaction vessel. It is preferred, however, to use as small an amount of catalyst as possible as this has an efiect on the molecular weight of the polymer obtained. As a rule, the catalyst concentration will range from about 0.1% to about 2% of the total monomer or monomers charged into the reactor.

The practice of this invention is illustrated by the following examples in which parts are by weight unless otherwise specified.

Example 1 A stainless steel pressure reactor is flushed with oxygen-free nitrogen and charged with 88 parts of anhydrous benzene and 0.35 part 0! a benzene solution of the heteropolyperoxide obtained by reacting equimolar proportions of acetone and methyl ethyl ketone and which contains 2.86% peroxide, calculated as hydrogen peroxide. This charge occupies about 25% of the volume of the reactor. After removal of the nitrogen by evacuation to constant pressure, the reactor is charged with ethylene to a, pressure of 165 atmospheres and heated to 125 C. Upon reaching this temperature the ethylene pressure is raised to 500-600 atmospheres and the polymerization is allowed to proceed with agitation for an 18-hour period.

acetone and methyl ethyl ketone. The'charge occupies about 25% of the reactor space. After removal of the nitrogen by evacuation to constant pressure, the reactor is charged with ethylene to a'pressure of 160 atmospheres and heated to 125 C. Upon reaching this temperature the ethylene pressure is raised to 850 to 950 atmospheres and the polymerization is allowed to proceed with agitation for a 14-hour .period. As the ethylene polymerizes the system is kept between 850 and 950 atmospheres pressure by periodically repressuring with ethylene. A total pressure drop of about 620 atmospheres is observed. The reactor is cooled and the excess ethylene is bled ofi. There is obtained 41 parts of white solid tough ethylene polymer which possesses a tensile strength or 3,720 lbs/sq. in. at 480% elongation, a tear resistance of 111 (cellophane units), and a solubility in excess of 20% by weight in xylene at 100 C. The intrinsic viscosity of the polymer is 1.22 (measured as a 0.125% solution in xylene at 85 C.), which corresponds to a molecular weight of about 22,000.

Example 3 v vheated to 120 C. Upon reaching thi tempera- I I We the Pressure is raised to 850-950 atmos heres and the polymerization is allowed to proceed with agitation for a 13-hour period. As the ethylene polymerizes the system is kept at'850-950 atmospheres pressure by periodically repressuring with ethylene. The total pressure drop is about 350 atmospheres. The reactor is cooled and the excess ethylene is bled ofl. There is obtained 24 parts of a white solid ethylene polymer which has an intrinsic'viscosity of 1.28 (measured as a 0.125% solution in xylene at 85 0.), which As the ethylene polymerizes, the system is kept corresponds to a molecular weight of about 23,300. This polymer has a. tensile strength of 3,250 lb./sq. in. at 490% elongation.

Example 4 A stainless steel pressure reactor is flushed with oxygen-free nitrogen and is charged with 88 parts of anhydrous benzene and 0.2 part of 3,6-diphenyl-s-tetroxane \C H-CIH5 volume. After removal of the nitrogen by evac- I uation to constant'pressure, the reactor is charged with ethylene to a pressure of 50 atmospheres and heated to 200 C. Upon reaching this temperature the ethylene pressure is raised to, 850-950 atmospheres. The polymerization is then allowed tained at 200 C. The reaction mixture is let -,down to essentially atmospheric pressure by to proceed with agitation for an 18-hour period.-

intrinsic viscosity of 0.89 (measured as a 0.125%- solution in xylene at 85 C.), which corresponds to a molecular weight of about 15,800. This polymer is tough, possessing a tensile strength of means of a control valve and the gaseous phase consisting of unreacted ethylene together with benzene and water vapor is separated. Excess water is removed from the wet solid product and the latter is dried yielding 4.4'lbs./hr. dry product corresponding to 47% ethylene conversion.

In some instances itmay be desirable to replace the organic medium by water or to use a mixture of water .and' an organic solvent such 'as benzene. Suitable organic media in addition to benzene includev isooctane, toluene, alcohols, such as tert.-'butyl alcohol, ethers, etc.

Bulk polymerization in the absence of an inert medium may also be employed. It is preferable to use reagents as pure as is commercially 2,263 lb./sq. in at 620% elongation, is relatively free of grain, and is very extrudable possessing an extrusion rate of 1.376 g./min./190 C./100 lb.

the same pressure.

through a cooler and pumped at 1000 atms. pres-- nitrogen pressure through a 1%" orifice.

Example 5 A. Catalyst preparation.-Thirty grams con-,

centrated sulfuric acid is added to 13g. distilled water and the solution is cooled to 25 C. 11.3 g. hydrogen peroxide is added and the mixture is cooled to 30 C. A mixture of 2.9 g. acetone and 3.6 g. methyl ethyl ketone is added slowly with stirring while the temperature is maintained below -15 C. 100 g. distilled water is added followed by 87 g. benzene. The layers are separated and the oil layer is washed with water until free from acid and ketones. Analysis of-the oil layer indicates a peroxide content of- 1.2% calculated as hydrogen peroxide. y

B. Polymerization in benzene-4.4 g. per hour of the catalyst solution prepared above isv dissolved in 8.6 lbs/hr. benzene and the resulting solution is pumped to approximately 60 atms. pressure and mixed with 3.8 lbs/hr. ethylene at The mixture is passed sure through a tubular preheater and thence, through a tubular reactor 17.5 ft. long and'i'c" I. D. J aokets on both preheater and reactor are maintained at 160 C. The reaction mixture is continuously removed from the reactor and is released by means of a control valve to a separater at essentially atmospheric pressure wherein unreacted ethylene and a portion of the benzene are separated as a gaseous phase. Most of the remaining benzene is. steamed from the solid product and the latter is dried yielding 0.12 lb./hr. correspondin to an ethylene conversion of 3.2%.

Example 6 A. Catalyst preparation-The procedure described in Example 5 is essentiallyduplicated except that 10% more hydrogen peroxide is used. Analysis of the catalyst solution indicates a peroxide content of 1.9% calculated as hydrogen peroxide. i

B, Polymerization in water-benzene.-Two streams are continuously iniecte'd into the .re-

actor. The first consisting of 30 g. per hour oi! the above catalyst solution, 8.5 lbs/hr. of benzene and 9.35 lbs/hr. ethylene is mixed and pumped to 1000 atms. pressure as describedin Example 5 and is preheated to 90 C. The second stream consisting of 21 lbs./hr. water is pumped to 1000 atms. and preheated to 244 C. The two streams are mixed and passed through a tubular refeasible. In general, the process is operated under conditions such that the molecular oxygen content of the ethylene is less than 1000 parts per million with 200 parts per million being preferred andunder 20 parts per million giving attractive products.

The present invention provides a class of catalysts for the polymerization of ethylene and other compounds containing monoethylenic unsaturation which can be easily prepared and used in small quantities and oiIer no serious purification problems. They are efiective over a wide range of temperatures and pressures and are active in the presence of a variety of materials.

The organic polyperoxides usedin the practice of this invention, are operable at temperatures which may be as low as C. and as high as 400 C. It is generally preferred, however, to operate at temperatures in the range of 120 to 250 C. and pressures in excess of atmospheric. In general, pressures in excess of 4 atmospheres can be used but the usual pressures employed are in the range 01' 200 to 3000 atmospheres.

. As a rule, the use of higher pressures permits the use of lower temperatures. The particular conditions of temperature and pressure in any one case are determined not only by the particular organic polyperoxide used but also by the material being polymerized. Temperatures and pressures are interdependent variables and the conditions for optimum results in anyone in-' stance have to be determined experimentally.

The present organic polyperoxide catalysts do not have induction periods, are rapid and enduring in their activity, and the limit of their eflectiveness is reached only when the free space in the reactor is completely occupied with products through a reaction zone or by pumping the reactants separately through a reaction zone and introducing the catalyst in solution or suspension immediately prior to entering the reaction zone. In a continuous process the catalyst solution or suspension can be introduced at intermediate stages throughout the reaction zone, since by this means the heat developedin any one portionof the apparatus is rapidly dissipated and consequently the polymerization can be carried through actor 49 it. long and I. D. with jacket main 7; to a desired high molecular weight product. The

present process is exothermic in character, and. as in any process where the amount of heat to be removed is large, a continuous process permits greater precision in control and consequently more uniformly excellent results.

.The catalysts of this invention are operable in the absence of agitation but in many instances good agitation is conducive to good yields of polymer. v

The products of this invention are useful for hot-dipped and melt-spray application, for conversion to wrapping foils. films. fibers, monofiis, electrical and thermal insulating materials, rigid and collapsible tubing, filaments. protective coat-' ings, and for many other purposes well known I to the art.

The term polymer is used herein in a generic sense to refer to the macromolecular products obtained by polymerizing one or more Organic compounds containing a polymer producing linkage.

I claim:

1. In a process involving the polymerization of ethylene at a temperature between 60 and 400 C. and at a pressure between 200 and 3000 atmospheres, the step which comprises conducting the polymerization in the presence of a heteropolyperoxide from acetone and a different ketone.

2. In a process involving the polymerization of ethylene at a temperature between 60 and 400 C. and at a pressure between 200 and 3000 atmospheres, the step which comprises conducting the I 8 v ethylene at a temperature between 00v and 400 C; and a pressure between 200 and 3000 atmospheres, the step which comprises conducting the polymerization in the presence of from about 0.001 to 5% of a heteropolyperoxide from acetone and methyl ethyl ketone based on the total weight-o1 monomers charged into the reactor.

5. In a process involving the polymerization of ethylene at a temperature between and 400 C. and at a pressure between 200 and 3000 atmos pheres, the step which comprises conducting the polymerization in the presence of a heteropolyperoxide from acetone and cyclohexanone.

6. A process for the preparation of cxtrudable polymers of ethylene which comprises polymerizing ethylene at a temperature between and 250 C. at a pressure between 200 and 3000 atmospheres, in the presence of a polyperoxide from acetone and cyclohexanone and 'a non-polymerizabie inert organic liquid medium.

MILTON J. ROEDEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENIB o'rnna REFERENCES 'Reiche: Die Bedeutung der Organishen Peroxyde, etc.," Sammlung Chem. 11. Chem-Tech.

Vortrage; Neue Folge, 34, pages 10 and 11 espe- 4. In a process involving the polymerization of Ser. No. 307,933, Moser (A. P. 0;), published June 15, 1943. 

1. IN A PROCESS INVOLVING THE POLYMERIZATION OF ETHYLENE AT A TEMPERATURE BETWEEN 60 AND 400*C. AND AT A PRESSURE BETWEEN 200 AND 3000 ATMOSPHERES, THE STEP WHICH COMPRISES CONDUCTING THE POLYMERIZATION IN THE PRESENCE OF A HETEROPOLYPEROXIDE FROM ACETONE AND A DIFFERENT KETONE. 